Vortex Meter – What Is Piping

The Vortex Flow Meter is one of the various types of volume flowmeters that are used frequently in the oil and gas industry to measure the flow inside a pipe. This device performs its best where introducing moving parts poses a problem. The main advantages of Vortex flow meters is that Sensitivity to process conditions variations are low low wear compared to other types as there are no moving parts and applicable for a wide range of fluids, i.e. liquids, steam, and gases. Working Principle of Vortex Flow Meter Vortex meters are frequency meters that work based on the vortex principle. A bluff body (disturbing element) is placed in the middle of the pipe inside each vortex flowmeter that disturbs the flow causing an obstruction. In the downstream of the obstruction, a mechanical sensor is placed which can measure the pressure differences (frequency) in the flowing fluid. Fig. 1: Typical Vortex Meters Components of Vortex Meter On average, every vortex meter consists of following electronics parts- Pick-up elements, MicroprocessorAC-pre amplifiers, Noise abatement features, AC-amplifier with filters, Schmitt Trigger, Factors affecting vortex Meter Performance In general, Vortex Meter performance is influenced by corrosion of upstream pipingsheddar bar geometry change due to erosion or wax depositspositional changes of sheddar bar when improperly securedHydraulic noise, etc. Important Features of the Vortex meter It provides a linear digital (or analog) output signal simplifying equipment installation as the use of separate transmitters or converters are not required. The accuracy of the meter is quite good over a wide flow range. However, this range is dependent upon operating conditions. The shedding frequency is a function of the bluff body dimensions. Being a frequency system, There is no drift. In the absence of any moving or wearing components, It provides improved reliability and reduced maintenance. Also, there are no manifolds or valves to cause leakage which in turn results in safe installation even for hazardous or toxic process fluids. For the sensors with high sensitivity, the same vortex meter can easily be used for both gas and liquid services. Additionally, whether the meter is being used on gas or liquid medium the vortex meter calibration is virtually independent of the process conditions like density, pressure, viscosity, temperature, etc. It comes with a low installation cost for pipes less than 6-inch size. However, meters above 12 in. (300 mm) have high cost compared to an orifice system and their limited output pulse resolution. Meters below 0.5 in. (12 mm) diameter is not practical. Vortex Flow Meter Selection and Sizing The operating conditions (process fluid temperature, ambient temperature, line pressure, and so on) should be comparable with the meter specification.With respect to chemical attack and safety, the meter wetted materials (including bonding agents) and sensors should be compatible with the process fluid.The vortex meter maximum and minimum flow rates for the specified application need to be established.Consequently, the flow range for any application depends totally upon the operating fluid viscosity, density, and the vapor pressure, and the application's maximum flow rate and line pressure. Advantages of Vortex Meter Applicable for liquids, gases, and steamLow wear low installation and maintenance costs.Low sensitivity to variations in process conditionsLong term accuracy and repeatabilityWide process temperature range applicabilityApplication on a variety of pipe sizes. Vortex Flow Meter Limitations Not suitable for very low flow ratesNot recommended for batching or intermittent flow applicationsMinimum upstream and downstream straight length requirementNot suitable for sludge and slurry services.Not suitable for Multiphase flow. Vortex Flow Meter Applications Vortex flowmeters work best with clean, low-viscosity and medium to high-speed fluids. Some of the main uses include: General water applicationsLiquid chemicals & pharmaceuticalsNatural gas meteringSteam measurementThe flow of liquid suspensions Types of Vortex Flow Meter Sensors The vortex flowmeter has a bluff body inside it to create vortices. The Sensors measure these vortices to calculate the equivalent flow rate. Various types of sensors are available as listed below Mechanical sensorThermal sensingCapacitive sensorPiezoelectric sensorStrain gauge sensorUltrasonic sensor Installation Recommendations Before installing a vortex flowmeter flow range must be known.A well-developed and symmetrical flow velocity profile, free from any distortions or swirls is required for Vortex flow meters. For this reason, most vortex flowmeter manufacturers recommend a minimum of 30 pipe diameters (D) downstream of control valves and 3 to 4 pipe diameters between the meter and downstream pressure taps. Temperature elements should be small and located 5 to 6 diameters downstream. For oversized process piping, concentric reducers and expanders may be required. These can be installed vertically, horizontally, or at any angle, but the pipe has to be kept in a flooded condition. Mating flanges should have the same diameter and smooth bore as the flowmeter. Weld neck flanges are preferred, and reducing flanges should not be used. The inner surface of the mating pipe should be free from mill scale, pits, holes, reaming scores and bumps for a distance of 4 diameters upstream and 2 diameters downstream of the meter. The bores of the meter, the gaskets, and the adjacent piping must be carefully aligned to eliminate any obstructions or steps. The piping on both sides of the meter should be properly supported to eliminate excessive pipe vibration.